On December 16, 2015, the International Court of Justice (Court) issued its decision[3] in the joined cases concerning Certain Activities carried out by Nicaragua in the Border Area (Costa Rica v. Nicaragua) and Construction of a Road in Costa Rica along the San Juan River (Nicaragua v. Costa Rica). According to the press release[4], Costa Rica alleged “that Nicaragua invaded and occupied Costa Rican territory, that it dug a channel thereon, and that it conducted works (notably dredging of the San Juan River) in violation of its international obligations,” while Nicaragua instituted proceedings against Costa Rica for the alleged breach of procedural and substantive obligations relating to the construction of a road along the San Juan river. Regarding Costa Rica’s argument, the Court found that “the activities carried out by Nicaragua in the disputed territory since 2010, including the excavation of three caños [channels] and establishment of a military presence in parts of that territory, were in breach of Costa Rica’s territorial sovereignty, and that Nicaragua consequently incurs the obligation to make reparation for the damage caused by its unlawful activities on Costa Rican territory.” In order to determine the parties’ claims to the area in questions, the Court “recall[ed] that the Parties concluded a Treaty of Limits in 1858 (hereinafter the ‘1858 Treaty’), which fixed the course of the boundary” and was affirmed by “the 1888 Arbitral Award of United States President Grover Cleveland.” Regarding Nicaragua’s alleged breach of its procedural obligations, the Court found that no environmental impact assessment (EIA) was necessary, since the “the dredging programme was of a limited scope and [did not] give rise to a risk of significant transboundary harm.” Since no assessment was required, Nicaragua had no duty to notify and consult with Costa Rica. The Court further found that since Costa Rica had produced no evidence that “the dredging programme caused harm to its wetland or resulted in a significant reduction in the flow of the Colorado River,” Nicaragua “had not breached its obligations concerning prevention of transboundary harm.”

Turning to Nicaragua’s claims, the Court found that “the construction of the road by Costa Rica carried a risk of significant transboundary harm [and] [t]herefore, the threshold for triggering the obligation to evaluate the environmental impact of the road project was met.” The Court determined that Costa Rica had “not shown the existence of an emergency that could potentially justify constructing the road without undertaking an environmental impact assessment.” The Court noted that “the studies carried out by Costa Rica were post hoc assessments which evaluated the environmental impact of stretches of the road already built, not the risk of future harm” and were thus not in compliance with EIA requirements. Further, “since Costa Rica has not complied with its obligation to perform an environmental impact assessment prior to the construction of the road, the Court cannot determine whether Costa Rica was required under general international law to notify, and consult with, Nicaragua.” Turning to the “obligation to exercise due diligence to prevent causing significant transboundary harm,” the Court “note[d] that the amount of sediment due to the construction of the road which is delivered to the river is at most 2 per cent of the river’s total load,” which could not be characterized as “significant harm.” It further found that “Nicaragua has not shown that sediment due to the construction of the road has caused significant harm to the morphology and navigability of the San Juan River and the Lower San Juan, that such sediment significantly increased Nicaragua’s dredging burden, or that the construction of the road has caused significant harm to the river’s ecosystem, its water quality or caused any other harm,” therefore concluding that “Nicaragua has not proved that the construction of the road caused significant transboundary harm.” Finally, the Court addressed “Nicaragua’s claim that the dumping of sediment and creation of sediment deltas constituted a violation of its territorial integrity and sovereignty over the San Juan River” and decided that “Costa Rica did not exercise any authority on Nicaragua’s territory and did not carry out any activity thereon.”